What is an emergency stop (E-stop) device and how should it be wired in a control circuit?

• A. An E-stop is a normally open stop switch that energizes the circuit when pressed.
• B. An E-stop is a normally closed stop switch that immediately de-energizes the control circuit when pressed, ensuring rapid shutdown.
• C. An E-stop is a fuse that opens on overload.
• D. An E-stop is a device that delays shutdown.

Answer: (C)

An emergency stop is a normally closed pushbutton that, when pressed, opens the circuit to immediately de-energize the control circuit. It is wired in series with the control power feeding the coil of the contactor (or other control relay), so pressing it interrupts the control power right away and stops the equipment. It’s not a fuse or a device that delays shutdown—the fuse protects against overload, not provide an operator-initiated, instantaneous stop. If the switch were normally open, pressing it wouldn’t interrupt the circuit, and a delay-type device wouldn’t meet the requirement for an immediate halt.